The Center for Craniofacial Molecular Biology will include an Animal Core Facility to support the research efforts of the center investigators. The four projects all require the use of experimental animals to complete the proposed studies examining mechanisms of craniofacial development. Mice at well defined stages of gestation, special strains of mice and transgenic mouse lines will be maintained in the vivarium facilities allocated by the University of Southern California Vivaria for use by the CCMB. The Animal Core will oversee all aspects concerning the housing, breeding and maintenance of the experimental animals used in the projects supported by the Center. The animal husbandry will be monitored to insure that temperature, light-dark cycles, cages, bedding materials, food, and water and numbers of animals per cage conform to the standards required and are optimal both to eliminate confounding variables in the experimental procedures and to provide reproducible source of tissue for experimentation. The colonies of mice will be bred under well controlled conditions with a 2 hour mating period and subsequent check for vaginal plugs. The control of breeding is essential to permit examination of tissues at defined points in gestation associated with the events in craniofacial development being studied in each of the four projects. The Animal Core will provide assistance to the investigators in staging the development of the embryos and fetuses (Theiler staging), in microdissection of the desired experimental tissues, in documentation of craniofacial malformations and in identifying animals with desired genotypic or phenotypic characteristics. The Animal Core will coordinate animal use so that the greatest use of the tissues from each experimental animal will occur. The mouse animal model systems will be used as paradigms for normal development as well as for identification of the etiology and molecular pathogenesis of congenital craniofacial malformations.